Conventional PTAC units are compact, self-contained cooling and heating systems commonly designed to fit within an opening in the wall of a building. One such conventional PTAC unit is sold under the name AIRXCEL, which is made by Suburban Manufacturing, as described at www.suburbanmanufacturing.com, the contents of which are hereby incorporated by reference. The front of the PTAC unit extends into the space to be conditioned, and the back of the PTAC unit extends through the wall opening to the outside of the building, allowing for the intake and exhaust of condenser and room ventilation air. The PTAC contains a sealed unitary refrigeration system, indoor and outdoor motor/blower assemblies, room cabinet with a discharge grille to discharge conditioned air into the room, and a controller to operate the unit in different modes and sense the room temperature.
PTAC units typically provide both heating and cooling, using electric power to cool and a variety of options for heating, including electric heat, reverse cycle heat pump, hydronic (hot water or steam) heat or gas heat. One disadvantage of PTAC units with the heating system integrated into the unit chassis is that the entire unit chassis needs to be removed when repair or replacement of only the heating or cooling system is needed.